damn, I found it finally... I had to add: glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP_EXT); glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP_EXT); glTexGeni(GL_R, GL_TEXTURE_GEN_MODE, GL_REFLECTION_MAP_EXT); after glTexImage2D I cannot see really why, and many tuts left that out...